Anti-Swelling, High-Strength, Anisotropic Conductive Hydrogel with Excellent Biocompatibility for Implantable Electronic Tendon

As hydrogels rapidly advance for diverse technologies, their practical applications as implantable artificial tendon becomes promising, yet challenging. It requires similar anisotropic fibril structures, matching water content, high mechanical strength, good biocompatibility, and stable performance under physiological conditions. Furthermore, the capabilities of real-time joint motion monitoring and implant condition are extremely important for the precise assessment of rehabilitation processes. However, it is challenging to realize all these properties simultaneously. Herein, this work reports an intelligent implantable artificial tendon based on strong and conductive anisotropic hydrogel, by coupling prestretching-induced ordered structure with drying-enabled strengthening. The fiber structure fixed during drying/rehydration produces a dense and stable network with a hierarchically anisotropic structure. The resulting anisotropic hydrogel presents excellent anti-swelling ability (<3%), high tensile strength (3.71 MPa), and toughness (9.86 MJ m(-3)) upon hydration, at a tendon-matching water content of 72.5 wt%. The in vitro and in vivo tests demonstrate its excellent biocompatibility with significant protein resistance. With reliable strain sensing, the hydrogel can act as an intelligent artificial tendon to restore and real-time monitor joint motion in an in vitro model. The SD rats with tendon defects display restored motor function after implantation of the hydrogel as tendon substitutes, facilitating malfunction tissue therapeutics and rehabilitation.